Active kids may be less prone to depression

NEW YORK (Reuters Health) - Studies have shown that exercise may battle depression in adults, and now new evidence suggests the same may be true for children.

In a study of nearly 4,600 middle-schoolers followed for two years, researchers found that the more active children were, the less likely they were to suffer symptoms of depression.

It's unclear whether this represents a cause-and-effect relationship, or whether feelings of depression caused some kids to become less active. But there is reason to believe that exercise helps thwart depression, according to one of the study's authors, Dr. Rod K. Dishman of the University of Georgia in Athens.

Along with studies suggesting active adults have a lower risk of developing depression down the road, there is evidence that exercise aids in the treatment of adult depression, Dishman told Reuters Health.

In addition, he explained, exercise seems to affect some key nervous system chemicals-norepinephrine and serotonin-that are targets of antidepressant drugs, as well as brain neurotrophins, which help protect nerve cells from injury and transmit nerve signals in brain regions related to mood.

Dishman and his colleagues report their findings in the journal Psychosomatic Medicine.

The study included 4,594 Minnesota seventh-graders who answered questions on their activity levels and other habits such as smoking and drinking. They also took a standard screening test for depression symptoms. The measures were repeated at the end of seventh grade and again at the end of eighth grade.

The researchers were interested in how changes in exercise habits over the two years were related to changes in depression scores. They found that overall, when activity levels increased, depression symptoms decreased, and when exercise levels declined, depression scores went up.

Dishman said that exercise could plausibly help prevent depression in the first place, as well as treat it. In their report, he and his colleagues point to recent clinical trials in which exercise, antidepressants and psychological therapy all had similar benefits for adults with depression-although, Dishman noted, the benefits of exercise generally took longer to emerge compared with drug treatment.

With adolescents, the researchers write, the safety of drug treatment is not yet certain, and since psychological therapy is not always effective, it will be important to keep studying potential "low-risk" alternatives, such as physical activity.